Caput mortuum

<h1 id="firstHeading" class="firstHeading" lang="en">Caput mortuum</h1>

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<p><i><b>Caput mortuum</b></i> (plural <i><b>capita mortua</b></i>) is a <a href="https://en.wikipedia.org/wiki/Latin_term" class="mw-redirect" title="Latin term">Latin term</a> whose literal meaning is "dead head" or "worthless remains",<sup id="cite_ref-1" class="reference"><a href="https://en.wikipedia.org/wiki/Caput_mortuum#cite_note-1">[1]</a></sup> used in <a href="https://en.wikipedia.org/wiki/Alchemy" title="Alchemy">alchemy</a> and also as the name of a <a href="https://en.wikipedia.org/wiki/Pigment" title="Pigment">pigment</a>.</p>

<h2>Alchemy and chemistry</h2>

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<div class="thumbcaption">Alchemical symbol for <i>Caput mortuum</i></div>

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<p>In alchemy, <i>caput mortuum</i> (alternately called <i><a href="https://en.wikipedia.org/wiki/Nigredo" title="Nigredo">nigredo</a></i>) signified a useless substance left over from a chemical operation such as <a href="https://en.wikipedia.org/wiki/Sublimation_%28chemistry%29" class="mw-redirect" title="Sublimation (chemistry)">sublimation</a> and the epitome of decline and decay; alchemists represented this residue with a stylized human skull, a literal death's head.<sup id="cite_ref-eastaugh_2-0" class="reference"><a href="https://en.wikipedia.org/wiki/Caput_mortuum#cite_note-eastaugh-2">[2]</a></sup>

The symbol shown on this page was also used in 18th-century chemistry to mean <i>residue</i>, <i>remainder</i> or <i>residuum</i>. <i>Caput mortuum</i> was also sometimes used to mean <i>crocus metallorum</i>, i.e. brownish-red metallic compounds such as <i>crocus martis</i> (<a href="https://en.wikipedia.org/wiki/Ferrous_sulphate" class="mw-redirect" title="Ferrous sulphate">ferrous sulphate</a>), and <i>crocus veneris</i> (<a href="https://en.wikipedia.org/w/index.php?title=Copper_oxidule&action=edit&redlink=1" class="new" title="Copper oxidule (page does not exist)">copper oxidule</a>).<sup id="cite_ref-3" class="reference"><a href="https://en.wikipedia.org/wiki/Caput_mortuum#cite_note-3">[3]</a></sup></p>

<h2>Pigment</h2>

<p><i>Caput mortuum</i> (variously spelled <b>caput mortum</b> or <b>caput mortem</b>), also known as <b>cardinal purple</b>, is the name given to a purple variety of <a href="https://en.wikipedia.org/wiki/Hematite" title="Hematite">haematite</a> <a href="https://en.wikipedia.org/wiki/Iron_oxide" title="Iron oxide">iron oxide</a> pigment, used in <a href="https://en.wikipedia.org/wiki/Oil_painting" title="Oil painting">oil paints</a> and paper <a href="https://en.wikipedia.org/wiki/Dye" title="Dye">dyes</a>. It was a very popular colour for painting the robes of religious figures and important personages (e.g. art patrons).

The name for this pigment may have come from the alchemical usage, since iron oxide (rust) is the useless residue of oxidization. It was originally a byproduct of <a href="https://en.wikipedia.org/wiki/Sulfuric_acid" title="Sulfuric acid">sulfuric acid</a> manufacture during the 17th and 18th centuries, and was possibly an early form of the <a href="https://en.wikipedia.org/wiki/Copperas" class="mw-redirect" title="Copperas">copperas</a> process used for the manufacture of <a href="https://en.wikipedia.org/wiki/Venetian_red" title="Venetian red">Venetian red</a> and <a href="https://en.wikipedia.org/w/index.php?title=Copperas_red&action=edit&redlink=1" class="new" title="Copperas red (page does not exist)">copperas red</a>.<sup id="cite_ref-4" class="reference"><a href="https://en.wikipedia.org/wiki/Caput_mortuum#cite_note-4">[4]</a></sup>

<i>Caput mortuum</i> is also sometimes used as an alternative name for <a href="https://en.wikipedia.org/wiki/Mummy_brown" title="Mummy brown">mummy brown</a> (alternatively Egyptian brown), a pigment that was originally made in the 16th and 17th centuries from ground-up <a href="https://en.wikipedia.org/wiki/Mummy" title="Mummy">mummies</a>, and whose use was discontinued in the 19th century when artists became aware of its ingredients.<sup id="cite_ref-5" class="reference"><a href="https://en.wikipedia.org/wiki/Caput_mortuum#cite_note-5">[5]</a></sup></p>

Caput mortuum

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